I have a 78 245 DL with an owner installed cruise control that cost
119.95 in 1978 when it was installed. I repaired it when I purchased it from the original owner by replacing the original relay (whose coil had burned out) with a not exact but equivalent replacement. It worked several years after that, but has finally quit again.My troubleshooting indicates that it is probably the totally analog "Speedostat" controller unit. This unit has an input and an output for a speedometer cable to reference vehicle speed, and an input and output vacuum tube that goes to a vacuum servo. After all, the 78 Volvos had no computer controlled anything.
I'm looking for a way to repair, but I fear that the speedostat unit is obsolete. I'm planning on a trip to some upick yards for a look-see. I think that that part may also be used on other cars besides Volvos.
I'd also like to consider a newer electronic unit, provided that it has similar signals to the analog unit, so I can use my existing turn signal stalk speed control switches and existing under the dash wiring. Since I have a manual transmission, I could get the vehicle speed sensing from the tach (or ignition). I'll never use the speed control except in 4th or 4th with OD, so the clutch switch will kill the speed references between switches between OD in and out, as I always clutch with OD in or out.
Does anyone have any experiences with fixing or refitting cruise control to older Volvos before the electronic injection?